JP2001329326A - Fin material for brazing - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an Al-Ni-Fe alloy fin material excellent in strength and thermal conductivity and also having high corrosion resistance. SOLUTION: This aluminum alloy fin material for brazing is composed of an aluminum alloy having a composition containing, by weight, >0.1 to 3% Ni, >1.5 to 2.2% Fe and <=1.2% Si, further containing at least one kind selected from the groups consisting of <=4% Zn, <=0.3% In and <=0.3% Sn, moreover containing, at need, one or more kinds selected from <=3.0% Co, <=0.3% Cr, <=0.3% Zr, <=0.3% Ti, <=1% Cu, <=0.3% Mn and <=1% Mg, and the balance aluminum with inevitable impurities, in which the ratio of the length in the vertical direction to the rolling direction of the crystal grains viewed from the sheet surface to the length in the parallel direction to the rolliig direction (the length in the vertical direction/the length in the parallel direction) is <=1/30, its electrical conductivity is controlled to 50 to 55% IACS, and tensile strength to 170 to 280 MPa.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fin material for brazing Al-Ni-Fe alloys having excellent corrosion resistance, strength and thermal conductivity.

[0002]

2. Description of the Related Art Most heat exchangers for automobiles use Al and A.
1 alloy is used and manufactured by the brazing method. Usually, Al-Si-based brazing material is used for brazing, so brazing is performed at a high temperature of about 600 ° C. In a heat exchanger such as a radiator, for example, as shown in FIG. 1, thin fins (2) formed into a corrugated shape are integrally formed between a plurality of flat tubes (1), and both ends of the flat tubes (1) are It is open to the space formed by the header (3) and the tank (4), and sends the high-temperature refrigerant from the space on one tank side to the space on the other tank (4) side through the flat tube (1). The heat exchange between the tubes (1) and the fins (2) causes the low-temperature refrigerant to circulate again.

In recent years, heat exchangers are becoming lighter and smaller, and for that purpose, it is necessary to improve the heat efficiency of the heat exchanger, and it is desired to improve the heat conductivity of the material. In particular, improvement in the thermal conductivity of the fin material is being studied, and a fin material of an alloy in which the alloy component is close to pure aluminum has been proposed as a heat conductive fin. However, when the fins are thinned, if the fins are not strong enough, there is a problem that the fins are crushed when the heat exchanger is assembled, or broken when used as a heat exchanger. In the case of a pure aluminum alloy fin, there is a drawback that the strength is insufficient, and the addition of an alloy element such as Mn is effective for increasing the strength. However, there is a problem that during brazing heating, elements added to the alloy for the purpose of improving strength are re-dissolved to inhibit the improvement of thermal conductivity during brazing.

As a fin material which solves these problems, Al-
An alloy in which Ni or Co is added to a Si-Fe alloy has been proposed, and exhibits properties having excellent strength and thermal conductivity (JP-A-7-216485, JP-A-8-10493).
No. 4). However, with these fin materials, 1.5%
(In the case of an aluminum alloy to which Ni is added together with Fe in excess of (% by mass; the same applies hereinafter), Al-Fe-Ni
Intermetallic compounds of the system are generated inside the fins, and these are factors that improve the strength and the thermal conductivity. However, there is a problem that the corrosion resistance of the fin material itself is reduced. The fin material protects the tube as a sacrificial anticorrosion material. However, if the fin material itself has a high corrosion resistance, the fin is not corroded at an early stage and the tube cannot be protected for a long time.

[0005]

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide an Al--Ni--Fe alloy fin material which is excellent in strength and thermal conductivity and has enhanced corrosion resistance.

[0006]

The object of the present invention has been attained by the following means. That is, the present invention relates to 0.1 wt%
Over 3 wt% Ni, over 1.5 wt% and 2.2
wt% or less Fe and 1.2 wt% or less Si, further 4 wt% or less Zn, 0.3 wt% or less I
2. At least one selected from the group consisting of n and 0.3 wt% or less of Sn, and if necessary, in addition to 3.
0 wt% or less Co, 0.3 wt% or less Cr, 0.3
wt% or less Zr, 0.3 wt% or less Ti, 1 wt%
The following Cu, 0.3 wt% or less Mn, 1 wt% or less Mg, contains one or more kinds, and is made of an aluminum alloy consisting of unavoidable impurities and the balance of aluminum. The ratio of the length in the direction perpendicular to the rolling direction to the length in the direction parallel to the rolling direction (length in the perpendicular direction / length in the parallel direction) is 1/30 or less, and the conductivity is 50%.
Not less than IACS and not more than 55% IACS, and a tensile strength of 17
An object of the present invention is to provide an aluminum alloy fin material for brazing, which is not less than 0 MPa and not more than 280 MPa.

[0007]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The feature of the present invention is that the corrosion resistance of the fin material itself is enhanced by controlling the metal structure using an alloy known to have excellent strength and electrical conductivity after brazing. is there. Before describing the control of the metallographic structure, the alloy elements targeted by the present invention will be described below. Here, more than 0.1 wt% and 3 wt% or less of Ni and 1.
The reason why Fe is contained in an amount of more than 5 wt% and not more than 2.2 wt% is to solve the problems of the fin material in which the strength and thermal conductivity after brazing are increased by adding Fe and Ni. Because it was Especially the amount of Fe is 1.5wt
The reason for limiting the alloy content to more than 1.5% is that if the content is 1.5 wt% or less, the deterioration of the corrosion resistance of the fin material itself is small, so that the metal structure of the present invention need not be particularly controlled. The reason why the upper limit of Fe is set to 2.2 wt% is that if the upper limit is exceeded, even if the method of the present invention is used, the corrosion resistance of the fin material cannot be improved. The lower limit of Ni is determined by the amount having the effect of improving the strength and conductivity by coexisting with Fe. If the upper limit of Ni exceeds the range of the present invention similarly to Fe, even if the method of the present invention is used, the corrosion resistance of the fin material cannot be improved.

Although the addition amounts of Ni and Fe are determined as described above, 0.6 wt% or more of Ni is added to secure high strength.
Is recommended, and particularly 0.9 wt% or more is recommended. In the case of using the continuous casting method when manufacturing the present fin material, Ni of 2 wt% or less is recommended for its stability. Further, Fe is particularly recommended to be 2.0 wt% or less in order to enhance the stability during continuous casting and further enhance the corrosion resistance of the fin material. In addition to the above Ni and Fe, 1.2 wt% or less of Si, 3.0 wt% or less of Co, 0.3 wt% or less of Cr, 0.3 wt% or less of Zr, and 0.3 wt% or less of T.
i, 4 wt% or less Zn, 0.3 wt% or less In,
0.3 wt% or less of Sn, 1 wt% or less of Cu, 1.3
It may contain one or more of Mn of 1 wt% or less of Mn of 1 wt% or less and unavoidable impurities. These elements show important functions in properties when the alloy is used as a fin material. The action and the reason for limitation for each element will be described below.

[0009] The addition of Si improves the strength. In addition to improving the strength by solid solution hardening of Si itself, especially when coexisting with Fe, Ni and Co,
And has the effect of promoting the precipitation of Ni and Co. In the fin material of the present invention, it is important not to coarsen the Al-Fe intermetallic compound. When Si is added, the intermetallic compound is likely to precipitate, and since a large number of precipitates are deposited, the size of each intermetallic compound is smaller than that in the case where Si is not added. Such an effect of accelerating the precipitation is not sufficient when the content of Si is 0.03% by weight or less, and when the content exceeds 1.2% by weight, the fins are melted at the time of heating by brazing. Therefore, when adding Si, it exceeds 0.03 wt% and exceeds 1.2%.
wt% or less.
The effect increases when the content is 3 wt% or more. Further, when the amount of Si is excessively increased, the content of Si is desirably 0.8 wt% or less because the dissolved Si lowers the thermal conductivity of the fin. These, 0.3
Among 0.4 wt% to 0.8 wt%, especially 0.4 to 0.7 w
It shows stable characteristics with t% of Si.

Co has the same function as Ni. Therefore, when Co is added, the addition amount is more than 0.1 wt% and not more than 3.0 wt%, but in particular, 0.3 wt% to 2 wt%.
% In the range. However, compared to Ni, Co has a slightly lower thermal conductivity and a weaker effect of dividing Al-Fe-based compounds. It is a metal that is more expensive than Ni. In the present invention, it is possible to use Co instead of Ni or to simultaneously add Ni and Co.
It is recommended to add Ni because adding Ni alone has a greater effect on characteristics and cost. The lower limit of the amount of Co to be added is 0.1 wt%. However, this is the case when adding alone, and when adding in combination with Ni, it is possible to add even less. Addition of 0.3 wt% or less of Zr and Cr improves the strength and Zr coarsens the recrystallized grains of the fin material generated at the time of brazing, and has a function of preventing the fin from drooping and preventing the diffusion of the wax into the fin. To be added.
However, alloys to which Zr and Cr are added during continuous casting may cause clogging of the nozzle, making casting impossible. Therefore, it is desirable not to add Zr and Cr, and when it is added, addition of 0.08 wt% or less is particularly recommended.

The addition of 0.3 wt% or less of Ti is mainly for improving the strength. However, alloys to which Ti is added during continuous casting may cause clogging of the nozzle, making casting impossible. Therefore, T
It is desirable not to add i.
The addition of not more than wt% is particularly recommended. In addition, it may be added for the purpose of refining the cast structure, in which case,
The objective is sufficiently achieved with 0.02 wt% or less. 4wt%
The following Zn, In of 0.3 wt% or less, and Sn of 0.3 wt% or less are added in order to impart a sacrificial anticorrosion effect to the fin material. The amount to be added and the element to be added may be determined according to the anticorrosion properties and thermal conductivity required for the fin material. In and Sn exhibit a sufficient sacrificial effect with a small amount of addition,
It is expensive and there is a problem that the scrap of the alloy cannot be recycled to other alloy materials. Therefore, in the present invention, Z
The addition of n is recommended. As the amount of Zn added increases, the corrosion of the fin material itself is reduced, so 2 wt% or less is recommended, and in particular, 1 wt% or less is recommended. The lower limit may be determined according to the material of the anticorrosion partner, but it is usually desirable to add 0.3 wt% or more. In the present invention, Cu may be further added in some cases. Cu is added mainly to improve the strength. When it is added, if it is 0.05 wt% or less, there is no effect of improving strength. Further, when the addition amount is increased, the effect of reducing the sacrificial anode effect becomes stronger, so that the content is set to 1 wt% or less.
0.3 wt% or less is particularly recommended. Cu has the function of making the potential of the fin material noble and reducing the sacrificial anode effect,
When adding Cu, it is necessary to add together with any element of Zn, In, and Sn.

Mn may be added to improve the strength, but a small addition significantly reduces the thermal conductivity.
Therefore, the addition of Mn is 0.3 wt% or less,
It is desirable not to add. Mg may also be added to improve the strength, but in the case of NB brazing, it reacts with the flux, and in order to reduce the brazing property, when forming a fin material for NB brazing, Mg is added. No. In the case of vacuum brazing, Mg of 1 wt% or less is used. However, it is recommended not to add Mg because it evaporates during brazing and its effect is small. The inevitable impurities of the alloy used in the present invention and the elements added for reasons other than the above include B added together with Ti for refining the ingot structure, etc. If it is 0.03% or less, it may be contained. The fin material of the present invention has the above alloy composition and the ratio of the length of the crystal grains viewed from the plate surface in the direction perpendicular to the rolling direction to the length in the direction parallel to the rolling direction (length in the perpendicular direction / length in the parallel direction). One characteristic is that the electrical conductivity is 1/30 or less, the electrical conductivity is 50% IACS or more and 55% IACS or less, and the tensile strength is 170 MPa or more and 280 MPa or less.

First, the crystal grain size as viewed from the plate surface will be described. Usually, the fin material has a predetermined fin material thickness by performing cold rolling while undergoing annealing in the middle, but the crystal grain size after annealing and the subsequent cold rolling, the fin material before brazing, The crystal grain size is determined. Since the final cold rolling reduction of the fin material is usually 50% or less, if an equiaxed crystal grain size is formed by annealing, the crystal grain as viewed from the plate surface when the fin material is formed is obtained. The ratio of the length in the direction perpendicular to the rolling direction to the length in the direction parallel to the rolling direction (length in the perpendicular direction / length in the parallel direction) is １ ／ or more. Further, the ratio of the length in the direction perpendicular to the rolling of the crystal grains as viewed from the plate surface of the annealed crystal grains to the length in the direction parallel to the rolling direction (length in the perpendicular direction / length in the parallel direction) is 1/10. Even if it becomes, it becomes 1/20 or more when it becomes a fin material. On the other hand, in the present invention, the ratio of the length in the direction perpendicular to the rolling direction and the length in the direction parallel to the rolling direction of the crystal grains as viewed from the plate surface of the fin material (length in the perpendicular direction / length in the parallel direction) ) Is 1/30 or less, which is significantly different from the crystal grain structure of a normal fin material. Actually, in order to make the fin material having the crystal grain size of the present invention with the conductivity and the strength within the range of the present invention, fine precipitates are densely dispersed inside the crystal grains, and It is only when the grain boundaries have a pinned structure.
Here, the ratio (length in the perpendicular direction / length in the parallel direction) of the length in the direction perpendicular to the rolling direction and the length in the direction parallel to the rolling direction of the crystal grains as viewed from the plate surface of the fin material is 1/30. If it exceeds, the precipitates in the fin material are relatively coarse and sparsely dispersed. Therefore, even in the fin material after brazing, only coarse particles remain in the fin material, a local battery is formed around the coarse particles, and the corrosion life of the fin material itself is reduced. Further, in this case, since sub-grain boundaries are not stopped in the precipitate, recrystallization proceeds promptly during the heat of brazing, which also becomes a factor of coarsening the precipitated particles. On the other hand, the ratio of the length in the direction perpendicular to the rolling direction of the crystal grains as viewed from the plate surface of the fin material and the length in the direction parallel to the rolling direction (length in the perpendicular direction / length in the parallel direction) as a condition of the present invention. ) Is 1/30 or less, the precipitated particles are densely present. When the brazing heat is applied in such a state, especially when the brazing heat is applied, a large amount of precipitated particles are not present in the recrystallized grain boundaries, and the amount of intermetallic compound having a size that forms a local battery is reduced. The corrosion resistance is improved. Further, since the sub-grain boundaries are stopped in the precipitate, the precipitation is promoted at a temperature before reaching the vicinity of 500 ° C. of the heat of brazing, and the effect of finely dispersing the precipitated particles is obtained. The crystal grain size may be determined by observing the fin material with an optical microscope after etching and taking a photograph or performing image processing as it is. The ratio of the length in the perpendicular direction to the length in the parallel direction is 1 /. When it is less than 100,
The length in the direction parallel to the rolling direction is increased, and may exceed the field of view. In such a case, it is clear that the present invention is satisfied, so that it is not necessary to consider a value of 1/100 or less, especially, assuming that the value is 1/100 or less.

The electric conductivity is an index indicating the amount of the solid solution element in the aluminum alloy. The larger the amount of the solid solution element, the lower the electric conductivity. When the electrical conductivity is less than 50% IACS, the amounts of Fe and Ni dissolved in the fin material are large, and Fe and Ni precipitate at the recrystallized grain boundary generated when the fin material is heated by brazing. If the precipitation increases along the recrystallized grain boundaries of the fin after brazing, the corrosion along the crystal grain boundaries increases when corrosion occurs. In this alloy type fin material, there is often one crystal grain in the thickness direction, so if the corrosion progresses along the grain boundaries, the fins will crumble and fall apart even if the entire fin does not corrode. Corrosion life is reduced. If it exceeds 55% IACS, the amount of precipitation in the fin material will be too large, and the precipitated particles will re-dissolve during heat of brazing. At this time, since finer particles are more likely to re-dissolve in solid solution, only coarse particles remain in the fin material after brazing. Therefore, in the fin material after brazing, a local battery is formed mainly on coarse precipitate particles, and the corrosion life of the fin material itself is reduced. The electrical conductivity is used as an index of the thermal conductivity of the fin material, and the problem is the electrical conductivity after brazing. Since the heat of brazing is performed at a temperature of around 600 ° C., the heat of brazing indicates the function of solution treatment, and the amount of solid solution elements (conductivity) in the fin material after brazing is substantially equal to the alloy composition of the fin material. Depends on On the other hand, the conductivity before brazing varies greatly depending on the heat treatment conditions during the production of the fin material, and has no correlation with the conductivity after brazing. Tensile strength is an index indicating the amount of dislocation introduced into the fin material,
The greater the tensile strength, the greater the amount of dislocation. Tensile strength is 1
If it is less than 70 MPa, the introduced dislocation amount is too small, and the driving force for recrystallization becomes small. That is, the crystal grain boundaries are easily pinned by the precipitated particles at the time of recrystallization during the heat of brazing, and as a result, many precipitated particles are present at the crystal grain boundaries of the fin material after the heat of brazing, and the corrosion resistance of the fin material is increased. Decrease. If the tensile strength exceeds 280 MPa, the corrugated formability will be reduced, and it will not be suitable as a brazing fin material.

The fin material for brazing of the present invention achieves its object by satisfying all of the above crystal grain size, electric conductivity and tensile strength. This is because a desired metallographic structure cannot be obtained if any of these conditions is lacking. To add further,
The above explanation of the reason for limitation is based on the premise that the other two conditions are within the scope of the present invention, and if the other two conditions are not within the scope of the present invention, a state different from the description will occur. In order to obtain the crystal grain size, conductivity, and tensile strength of the present invention, after forming a coil of the above alloy by a continuous casting and rolling method, the coil is cold-rolled to a thickness of a fin material in a cold rolling step. Rolling is performed, and an optimal heat treatment may be performed during the rolling. The continuous casting and rolling method is a method of continuously casting a strip having a thickness of several mm from a molten aluminum alloy to produce a coil as it is, and the Hunter method is known as a typical method of the 3C method or the like. I have. Compared to the case of producing an ingot by DC casting and producing a coil with a thickness of several mm by hot rolling, the continuous casting and rolling method has a higher cooling rate during casting, so the intermetallic compounds are finely divided during casting. In the case of an alloy containing a large amount of Fe such as the present alloy, this is a method having an effect of improving strength. Furthermore, when the inventors studied,
In the continuous casting and rolling method, supersaturation of Fe is
It has been found that the corrosion resistance of the fin material itself can be enhanced because Ni and Ni form a solid solution.

In order to obtain the fin structure of the present invention, a coil is manufactured by continuous casting and rolling, and the coil is manufactured by a cold rolling process to obtain a fin material.
mm to a fin material.
Annealing at a temperature of 0 ° C. or more and 500 ° C. or less is performed twice or more.
At that time, the second annealing from the last is performed at 0.4 mm or more and 2 mm or less, and the final annealing can be performed under heating conditions under which recrystallization is not completed, whereby a target structure can be obtained. The above is one example for explaining the fin material of the present invention, and the present invention is not limited to this. The thickness of the fin material in the present invention is usually a thin material of 0.1 mm or less. The present invention relates to a brazing sheet fin having high strength and high thermal conductivity, and it is not necessary to use a fin material having high strength for a plate thickness exceeding 0.1 mm. The aluminum alloy fin material for brazing of the present invention can solve the problems of alloys known to have improved properties as fin materials for brazing. Here, the brazing may be the NB method, the VB method, or the like that has been conventionally performed, and the NB method is particularly recommended. This is because the NB method has better productivity.

【Example】

Hereinafter, the present invention will be described specifically with reference to examples. A coil having a width of 1000 mm and a thickness of 6 mm was produced from an aluminum alloy having the composition shown in Table 1 by continuous casting and rolling. Thereafter, a fin material having a thickness of 0.06 mm was formed by cold rolling. By changing various annealing conditions during the process, fin materials shown in Table 2 were produced. The roll diameter of the continuous casting and rolling mill used was 618 mm. As a comparison, a coil having a thickness of 6 mm was manufactured in the steps of DC casting, facing, and hot rolling, and then fin materials shown in Table 2 were also manufactured by cold rolling and annealing. The obtained fin material is heated at 600 ° C. for 3 hours.
After the addition of NB brazing heat for one minute, a CASS test was performed for one week to investigate the corrosion loss of the fin material. Table 3 shows the results.

[0018]

[Table 1]

[0019]

[Table 2]

[0020]

[Table 3]

As is evident from the results in the above table, the fin material of the present invention has a very small corrosion weight loss as compared with the comparative example.
The corrosion resistance of the fin material itself is excellent.

[0022]

As described above, according to the present invention, the corrosion resistance of the fin material itself of the Al-Ni-Fe alloy fin material known as a high strength and high heat conductive fin material alloy can be remarkably increased, which is industrially remarkable. It has a great effect.

[Brief description of the drawings]

FIG. 1 is a schematic diagram showing a radiator.

[Explanation of symbols]

 1 Tube 2 Fin 3 Header 4 Tank

Continued on the front page (72) Inventor Akira Kawahara 2-6-1, Marunouchi, Chiyoda-ku, Tokyo Inside Furukawa Electric Co., Ltd. (72) Inventor Atsushi Fukuda 1-1-1, Showa-cho, Kariya-shi, Aichi Prefecture DENSO Corporation (72) Inventor Yoshihiko Kamiya 1-1-1, Showa-cho, Kariya-shi, Aichi Prefecture Inside Denso Corporation (72) Inventor Maki Shimizu 1-1-1, Showa-cho, Kariya-shi, Aichi Prefecture Inside Denso Corporation (72) Inventor Kenji Nekura 1-1-1, Showa-cho, Kariya-shi, Aichi Prefecture Inside DENSO Corporation

Claims (1)

[Claims] 1. An N content exceeding 0.1 wt% and not more than 3 wt%.
i, containing 1.5 wt% or more and 2.2 wt% or less of Fe and 1.2 wt% or less of Si, and further containing Zn of 4 wt% or less, In of 0.3 wt% or less, and Sn of 0.3 wt% or less. Containing at least one member selected from the group consisting of:
In addition to this, if necessary, 3.0 wt% or less of Co, 0.1 wt% or less.
Cr of 3 wt% or less, Zr of 0.3 wt% or less, 0.3
wt% Ti or less, 1 wt% or less Cu, 0.3 wt%
The following Mn contains one or more kinds of Mg of 1 wt% or less, is made of an aluminum alloy composed of unavoidable impurities and the balance of aluminum, and has a length perpendicular to a rolling direction of crystal grains as viewed from the plate surface. The ratio of the length parallel to the rolling direction (length in the perpendicular direction / length in the parallel direction) is 1/30
Is less than or equal to 50% IACS and 55% IAC
S or less, tensile strength 170 MPa or more and 280 MPa
An aluminum alloy fin material for brazing characterized by the following.